U.S. military leaders say they're working to keep troops in a number of key enlisted jobs, from cyber security to special operations to the nuclear force -- and may ratchet up incentives to do so.

The subject came up during a recent hearing of the House Armed Services Committee's Military Personnel Subcommittee, headed by Rep. Mike Coffman, a Republican from Colorado.

"So many times, I think, we talk ... more about the officer side of the equation, but on the enlisted side, what is a critical career field that it's difficult to -- I think accessions are not a problem I'm assuming, but -- to retain," he said.

Coffman directed the question to Marine Lt. Gen. Mark Brilakis, deputy commandant for Manpower and Reserve Affairs; Navy Vice Adm. Robert Burke, chief of naval personnel; Air Force Lt. Gen. Gina M. Grosso, deputy chief of staff for manpower, personnel and services; and Army Lt. Gen. James C. McConville, deputy chief of staff for personnel, who was recently tapped to become the service's vice chief of staff.

As the military looks to expand its ranks under the Trump administration, leaders may turn to bonuses or other incentives to keep some of the more than 1 million enlisted troops who make up almost 82 percent of the active force serving in these critical jobs.

Marine Corps: Cyber, Intel

Brilakis said cyber and intelligence fields, including human intelligence specialists and counter-intelligence specialists, "have been challenged with retentions," meaning the service has struggled to keep enough Marines in those jobs.

"Part of the challenge ... in cyber [comes from] what we call lat-move [military occupational specialties], so we take junior Marines from various MOSs in meeting those requirements because of very technical, very difficult training," he said.

"There are incentives that we use to attract those individuals," Brilakis added. "And we're taking a look at how we've contracted them in the past and how we'll do it in the future -- whether you finish the training, get your certification and then you serve out your contract length."

Navy: Nuclear, Linguist, Cryptology, Cyber, Electronics

"Our No. 1 challenge continues to be our nuclear-trained enlisted ratings," Burke said. "And then a very close tie there would be the linguists and the cryptology specialists." With almost identical vocational aptitude required for both types of jobs, "they're both a recruiting challenge and a retention challenge," he said.

On the retention front, "No. 3 and No. 4 after that would be cyber offense and defense, and then all the advanced electronics fields," Burke said. "We're managing all of those retention-wise with the SRBs [selective re-enlistment bonuses]. We are having to start to ratchet those numbers back up."

Air Force: Cyber, SpecOps, Intel, EOD, Nuclear

"On the enlisted side, we have actually unprecedented retention, with the exception of five career fields that we're following closely," Grosso said.